OXIDATION OF SILVER-PASSIVATED SI(111) - AG-(ROOT-3X-ROOT-3)R30-DEGREES

The interaction of unexcited, molecular oxygen with Si(111):Ag-(root 3 X root 3)R30 degrees and Si(111)-7 X 7 surfaces was studied by using soft X-ray (SXPS) and X-ray photoemission spectroscopy (XPS) as well a s low-energy electron diffraction (LEED). We observe a strong passivat ion of root 3 X root 3 surfaces against oxidation below exposures of 1 0(6) L (1 L = 10(-6) Torr s) with regard to what is observed at clean 7 X 7 surfaces. The oxidation seems to proceed in two stages which may be attributed to precursor-mediated dissociative chemisorption and el ectric-field-assisted diffusion, i.e., the Mott-Cabrera mechanism.